Flat-Profile Tape–Head Friction and Magnetic Spacing

2014 ◽  
Vol 50 (3) ◽  
pp. 34-39 ◽  
Author(s):  
Johan B. C. Engelen ◽  
Simeon Furrer ◽  
Hugo E. Rothuizen ◽  
Mark A. Lantz
2021 ◽  
pp. 089484532110172
Author(s):  
Ruth Noppeney ◽  
Anna M. Stertz ◽  
Bettina S. Wiese

Obtaining a doctorate offers various career options. This study takes a person-centered approach to identify interest profiles. Career goals (professorate, entrepreneur, etc.) were assessed at two time points (1-year interval) in a sample of doctoral students and doctorate holders from the STEM fields in German-speaking areas ( NT 1 = 2,077). Latent profile analysis revealed that a four-profile solution provided the best data fit: At T1, 33.0% of the participants aimed for a management position in industry, 16.9% pursued an academic career, 30.1% were interested in activities without leadership responsibilities, and 20.1% had a relatively flat career-goal profile. Latent transition analysis indicated that most changes occurred for those classified into the flat profile, while strong interest in a management career was very stable over time. Additionally, the attainment of the doctorate seemed to be a good predictor for profile membership: Doctorate holders were more likely to be clearly dedicated to an academic career.


Electronics ◽  
2021 ◽  
Vol 10 (15) ◽  
pp. 1802
Author(s):  
Eduardo Martinez-de-Rioja ◽  
Daniel Martinez-de-Rioja ◽  
Rafael López-Sáez ◽  
Ignacio Linares ◽  
Jose A. Encinar

This paper presents two designs of high-efficiency polarizer reflectarray antennas able to generate a collimated beam in dual-circular polarization using a linearly polarized feed, with application to high-gain antennas for data transmission links from a Cubesat. First, an 18 cm × 18 cm polarizer reflectarray operating in the 17.2–22.7 GHz band has been designed, fabricated, and tested. The measurements of the prototype show an aperture efficiency of 52.7% for right-handed circular polarization (RHCP) and 57.3% for left-handed circular polarization (LHCP), both values higher than those previously reported in related works. Then, a dual-band polarizer reflectarray is presented for the first time, which operates in dual-CP in the frequency bands of 20 GHz and 30 GHz. The proposed antenna technology enables a reduction of the complexity and cost of the feed chain to operate in dual-CP, as a linear-to-circular polarizer is no longer required. This property, combined with the lightweight, flat profile and low fabrication cost of printed reflectarrays, makes the proposed antennas good candidates for Cubesat applications.


2007 ◽  
Vol 129 (11) ◽  
pp. 1415-1421 ◽  
Author(s):  
Joseph Borowsky ◽  
Timothy Wei

An experimental investigation of a two-phase pipe flow was undertaken to study kinematic and dynamic parameters of the fluid and solid phases. To accomplish this, a two-color digital particle image velocimetry and accelerometry (DPIV∕DPIA) methodology was used to measure velocity and acceleration fields of the fluid phase and solid phase simultaneously. The simultaneous, two-color DPIV∕DPIA measurements provided information on the changing characteristics of two-phase flow kinematic and dynamic quantities. Analysis of kinematic terms indicated that turbulence was suppressed due to the presence of the solid phase. Dynamic considerations focused on the second and third central moments of temporal acceleration for both phases. For the condition studied, the distribution across the tube of the second central moment of acceleration indicated a higher value for the solid phase than the fluid phase; both phases had increased values near the wall. The third central moment statistic of acceleration showed a variation between the two phases with the fluid phase having an oscillatory-type profile across the tube and the solid phase having a fairly flat profile. The differences in second and third central moment profiles between the two phases are attributed to the inertia of each particle type and its response to turbulence structures. Analysis of acceleration statistics provides another approach to characterize flow fields and gives some insight into the flow structures, even for steady flows.


Author(s):  
Nasim Chitsaz ◽  
Kamran Siddiqui ◽  
Romeo Marian ◽  
Javaan S. Chahl

Abstract In this study, computational fluid dynamics analysis was performed on a three-dimensional model of a Libellulidae wing to determine aerodynamic performance in gliding flight. The wing is comprised of various corrugated features alongside the spanwise and chordwise directions, as well as twist. The detailed features of real 3D dragonfly wing models, including all the corrugations through both span and chord, have not been considered in the past for a detailed aerodynamic analysis. The simulations were conducted by solving the Navier-Stokes equations to demonstrate gliding performance over a range of angles of attack at low Reynolds numbers. The numerical model was validated against experimental data obtained from a fabricated corrugated wing model using particle image velocimetry. The numerical results demonstrate that bio-inspired wings with corrugations compared to flat profile wings generate more lift with lower drag, trapping the vortices in the valleys of wing corrugation leading to delayed flow separation and delayed stall. The experimental and numerical results demonstrate that the methodology presented in this study can be used to measure bio-inspired 3D wing flow characteristics, including the influence of complex corrugations on aerodynamic performance. These findings contribute to the advancement of knowledge required for designing an optimized bioinspired micro air vehicle.


2021 ◽  
Vol 8 ◽  
Author(s):  
Tomas Manik ◽  
Knut Marthinsen ◽  
Kai Zhang ◽  
Arash Imani Aria ◽  
Bjørn Holmedal

In the present work, the deformation textures during flat profile extrusion from round billets of an AA6063 and an AA6082 aluminium alloy have been numerically modeled by coupling FEM flow simulations and crystal plasticity simulations and compared to experimentally measured textures obtained by electron back-scatter diffraction (EBSD). The AA6063 alloy was extruded at a relatively low temperature (350°C), while the AA6082 alloy, containing dispersoids that prevent recrystallization, was extruded at a higher temperature (500°C). Both alloys were water quenched at the exit of the die, to maintain the deformation texture after extrusion. In the center of the profiles, both alloys exhibit a conventional β-fiber texture and the Cube component, which was significantly stronger at the highest extrusion temperature. The classical full-constraint (FC)-Taylor and the Alamel grain cluster model were employed for the texture predictions. Both models were implemented using the regularized single crystal yield surface. This approach enables activation of any number and type of slip systems, as well as accounting for strain rate sensitivity, which are important at 350°C and 500°C. The strength of the nonoctahedral slips and the strain-rate sensitivity were varied by a global optimization algorithm. At 350°C, a good fit could be obtained both with the FC Taylor and the Alamel model, although the Alamel model clearly performs the best. However, even with rate sensitivity and nonoctahedral slip systems invoked, none of the models are capable of predicting the strong Cube component observed experimentally at 500°C.


1970 ◽  
Vol 18 ◽  
pp. 119-129
Author(s):  
Kuswata Kartawinata ◽  
Eko B. Walujo

Pulau Rambut (± 56ha) is one of the islands of the Pulau Seribu group. It is a coral island covered by disturbed forest and secondary growth at the center, and mangrove forest at its periphery. A study in a 290 x 10 m transect running south to north across the mangrove forest shows a distinct zonation as follows : the Scyphiphora hydrophyllacea - Lumnitzera racemosa community on coral flat with patchy shallow soils on the interior, the Rhizophora mucronata community on relatively deep soil overlaying coral formation, and the R. mucronata - R. stylosa community on periodically submerged coral flat. Profile diagrams established along the transect show structural changes also. The R. mucronata forest is the most developed community and appears to be the most prevalent. R. stylosa forms the pioneer species on this island.


2021 ◽  
Vol 13 (17) ◽  
pp. 3391
Author(s):  
Zhipeng Sun ◽  
Xiaojing Niu

The coast around the Abandoned Yellow River Delta underwent significant changes under anthropogenic disturbance. This study aims to reveal the variation of the coastline, tidal flat area, and intertidal zone slope before, during, and after extensive reclamation during the period of 1984–2019 using satellite remote sensing images. In order to eliminate the influence of the varying water level, a new coastline correction algorithm had been proposed under the condition of insufficient accurate slope and water level data. The influence of seawalls on slope estimation were considered in it. The spatiotemporal evolution of coast had been analyzed and confirmed to be reasonable by comparing with the observed data. The results show that the coast can be roughly divided into a north erosion part and a south deposition part. Affected by reclamation, their tidal flat area in 2019 is reduced to only 43 and 27% of original area in 1984, respectively, which results in a continuous decrease in the tidal flat width. The adjustment of the tidal flat profile makes the slopes steeper in the erosion part, while the slopes in the deposition part remain stable. The reclamation has stimulated a cumulative effect as the disappearance of the intertidal zone, which may lead to the destruction of biological habitats.


Author(s):  
A. D. Walker ◽  
I. Mariah ◽  
D. Tsakmakidou ◽  
H. Vadhvana ◽  
C. Hall

Abstract To reduce fuel-burn and CO2 emissions from aero gas turbines there is a drive towards very-high bypass ratio and smaller ultra-high-pressure ratio core engine technologies. However, this makes the design of the ducts connecting various compressor spools more challenging as the higher required radius change increases their aerodynamic loading. This is exacerbated for the duct which feeds the engine core as it must accept the relatively low-quality flow produced by the fan root. This is characterised by a hub-low pressure profile and large secondary flow structures which will inevitably increase loss and the likelihood of flow separation. Additionally, the desire for shorter, lighter nacelles means that the engine intake may be unable provide a uniform inlet flow to the fan when the aircraft is at an angle of attack or subject to cross winds. Any inlet distortion this generates can also further degrade the quality of the flow entering the core of the engine. This paper uses a combination of experiments and CFD to examine the effects of the inlet flow on the aerodynamics of an engine section splitter and transition duct designed to feed the low-pressure spool of a high bypass ratio turbofan. A fully annular test facility incorporating a 1½ stage axial compressor was used to compare the system performance of a rotor that produced a nominally flat profile with one that had a notably hub deficient flow. A RANS CFD model, employing a mixing plane between the rotor and Engine Section Stator (ESS) and a Reynolds Stress turbulence model, was then validated and used to further investigate the effects of increased inlet boundary layer thickness and bulk swirl distortion at rotor inlet. Overall, changes to the inlet condition were seen to have a surprisingly small effect on the flow at duct exit — i.e. the flow presented to the downstream compressor. Changes to the inlet did, however, generate increased secondary flows and degrade the performance of the ESS. This resulted in notably increased total pressure loss; in excess of 12% for the hub-low inlet and in excess of 30% at high inlet swirl where the flow in the ESS separated. However, the increased ESS wake structures, and the enhanced mixing, delayed separation in the duct suggesting that, overall the design was reasonably robust, albeit with a significant penalty in system loss.


2016 ◽  
Vol 8 (3) ◽  
pp. 431-436 ◽  
Author(s):  
Duo Wang ◽  
Raphaël Gillard ◽  
Renaud Loison

This paper describes a linear-polarized reflector that reflects incident wave almost parallel to its surface at 60 GHz, when illuminated by an impinging plane wave with normal incidence. This structure is designed as a simple and low-cost passive repeater with both a quasi-endfire radiation and a flat profile. Working as a transmission relay, it is a quite potential and possible solution to improve the radio-coverage in the T-shaped corridor, which is a typical scenario of non-light-of-sight (NLOS) environment for 60 GHz indoor communications. The proposed repeater consists of an array of parallel grooves with appropriate depths, drilled in a metallic plate. Full-wave simulations and theoretical investigations are carried out to demonstrate the working principle and to optimize the performance. Then, an 80-groove breadboard in the size of 200 mm × 200 mm is fabricated and measured to explore the feasibility of the concept. In a practical measurement, when the distance from the repeater to transmitting antenna (Tx) is 2 m, and to the receiving antenna (Rx) is 1.5 m, the repeater exhibits a main beam at ±75° with gain up to 22.7 dB. The communication between Tx and Rx in NLOS areas is thus successfully recovered.


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